Your object contains member variables which are themselves not serializable 'ReportDataStoreRegion'. If you really want to serialize your object. One option would be to declare the variable as transient so that it is not serialized.

java.io.NotSerializableException: hudson.plugins.doxygen.DoxygenEnvironmentVariableExpander at java.io.ObjectOutputStream.writeObject0(Unknown Source) at java.io.ObjectOutputStream.defaultWriteFields(Unknown Source) at java.io.ObjectOutputStream.writeSerialData(Unknown Source) at java.io.ObjectOutputStream.writeOrdinaryObject(Unknown Source) at java.io.ObjectOutputStream.writeObject0(Unknown Source) at java.io.ObjectOutputStream.defaultWriteFields(Unknown Source) at java.io.ObjectOutputStream.writeSerialData(Unknown Source) at java.io.ObjectOutputStream.writeOrdinaryObject(Unknown Source) at java.io.ObjectOutputStream.writeObject0(Unknown Source) at java.io.ObjectOutputStream.writeObject(Unknown Source) at hudson.remoting.UserRequest._serialize(UserRequest.java:158) at hudson.remoting.UserRequest.serialize(UserRequest.java:167) at hudson.remoting.UserRequest.(UserRequest.java:63) at hudson.remoting.Channel.call(Channel.java:776) at hudson.FilePath.act(FilePath.java:980) at hudson.FilePath.act(FilePath.java:969) at hudson.plugins.doxygen.DoxygenArchiver._perform(DoxygenArchiver.java:223) at hudson.plugins.doxygen.DoxygenArchiver.perform(DoxygenArchiver.java:177) at hudson.tasks.BuildStepMonitor$2.perform(BuildStepMonitor.java:32) at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:779) at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:726) at hudson.model.Build$BuildExecution.post2(Build.java:185) at hudson.model.AbstractBuild$AbstractBuildExecution.post(AbstractBuild.java:671) at hudson.model.Run.execute(Run.java:1766) at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43) at hudson.model.ResourceController.execute(ResourceController.java:98) at hudson.model.Executor.run(Executor.java:381)